1. Field of the Invention
The present invention is related to grinding machines for turbine or impeller blades or similar.
2. Related Art
From publication U.S. Pat. No. 5,704,826, a turbine rotor blade grinding machine is known where the head has two grinding wheels with different features for grinding different rotors in view of the blade length and width. This machine avoids the substitution of a grinding wheel and having to repeat the adjusting process of the angular and linear position of the head of the new grinding wheel with respect to the new rotor, which it is necessary with the machines having a head with only one grinding wheel.
In the grinding machine described in publication U.S. Pat. No. 5,704,826, the angular and lineal displacements of the head to position the second grinding wheel are controlled by a control unit of the machine having a CNC, which calculates the coordinates of the new position starting from geometric data relative to the two grinding wheels, with the cooperation of an optical measuring system to line up the grinding wheel and measure the radius of the blade tips.
An example of an optical system to line up the grinding wheel and measure the blade radius during the grinding operation at high speed of the rotor, between 1500 r.p.m. and 3000 r.p.m., controlled by means of stroboscope is disclosed U.S. Pat. No. 4,566,225, in which the light intensity received at the sensor represents the height or radius of the blades, but here the optical sensor uses an infrared light beam.
To obtain the desired at the blade tips, the grinding wheel carries out micrometric incremental displacements of the grinding wheel head in both directions, axial and radial, with respect to the rotor during the grinding operation. The abrasion on the grinding wheel due to the use of the grinding wheel for grinding makes it necessary to compensate for the wear and to correct the irregularities of the surface of the grinding wheel by means of a shaping device. The superficial irregularities of the grinding wheel provoke the appearance of burrs at the blade tips, which affect the radius measuring of the blades, and can cause an excess of grinding.
In publication EP-0592112-A, the machine has a shaping device having a diamond roller, supported on a carriage. This machine has the inconveniences that the shaping device is separated from the grinding wheel head and situated behind the grinding wheel head. The shaping of the grinding wheel is executed once the grinding cycle of a rotor is finished, or at the interval of a grinding cycle, stopping the grinding operation, separating the head from its working position and moving the grinding wheel to the roller. After the shaping, the grinding wheel is adjusted again, and placed in contact with the blade tips to continue the grinding cycle.